Device for use in machines for manufacturing plastic foil covered paper

ABSTRACT

METHOD OF MANUFACTURING COVERED PAPER IN WHICH ONE SIDE OF THE EXTRUDED PLASTIC IS MAINTAINED AT A HIGH TEMPERATURE TO INSURE A GOOD BOND WITH THE PAPER AND THE OTHER SIDE IS COOLED RAPIDLY TO PREVENT OXIDATION.

' 1971 T. L. LINDH ETAL 3,556,85

DEVICE FOR USE IN MACHINES FOR MANUFACTURING PLASTIC FOIL COVERED PAPEROriginal Filed Febr 4, 1965 INVENTORS TORSTEN L. LINDH LARS O.l.LINDBLAD ATTORNEY United States Patent O 3,556,885 1 DEVICE FOR USE INMACHINES FOR MANUFAC- TURING PLASTIC FOIL COVERED PAPER TorstenLennartson Lindh, Lund, and Lars Olof Ingemar Lindblad, Sodra Sandby,Sweden, assignors to AB Tetra Pak; Lund, Sweden, a Swedish companyOriginal application Feb. 4, 1965, Ser. No. 430,420, now Patent No.3,440,125, dated Apr. 22, 1969. Divided and this application Aug. 19,1968, Ser. No. 753,665 Int. Cl. B29c 13/00 US. Cl. 156-244 1 ClaimABSTRACT OF THE DISCLOSURE Method of manufacturing covered paper inwhich one side of the extruded plastic is maintained at a hightemperature to insure a good bond with the paper and the other side iscooled rapidly to prevent oxidation.

This application is a division of U .S. patent application Ser. No.430,420, filed Feb. 4, '1965, now Pat. No. 3,440,- 125.

The present invention refers to a device for use in machines formanufacturing plastic foil covered paper and has as a principal objectto assist in providing an improved adhesion between the paper andthefoil of plastic.

A generally practised method for covering a paper web with a foil ofplastic is to advance the paper web across a rubber roll and through thenip between the latter and a cooling roll of metal, at the same time asthe foil of plastic is extruded from a nozzle provided thereabove anddirected downwardly, so that the foil will run down to meet thepaper-Web at the entrance to the nip. Provided that the foil of plasticis of sufliciently high temperature when applied to the paper web duringits passage between the rolls, it is bonded to the web with an ampleamount of adhesion. On its way on to the paper web, however, the hotfoil emerging from the nozzle is subjected to heat losses to theenvironment,so that the temperature of the foil may go down below thatrequired for obtaining the desired amount of adhesion between the foiland the paper web. To avoid this drawback it has been suggested toprevent the heat losses by mounting a heat reflecting metallic screen ateach side of the foil of plastic between the extruder nozzle and therolls. These two screens both assist in keeping the temperature in theenvironment of the foil of plastic at a higher level and to reflect heatback to the foil. Owing to the higher temperature of the foil thusachieved, another drawback is encountered, however, which consists inthe fact that the foil is subjected to oxidation.

As a result of the invention, it is achieved that the temperature of thefoil of plastic can be maintained at a high level on the side to bebonded to the paper web but kept at a low level on the other side, sothat the foil is not oxidized on this other side. The invention consistsin a device in which on either side of the path which a foil of plasticextruded from an extruder nozzle has to follow up to the point where itencounters a paper web there are 3,556,885 Patented Jan. 19, 1971provided a bright and a blackened screen, respectively, the brightscreen being on the side from which the paper web is intended to engagethe foil and the blackened screen is on the opposite side.

The invention will be explained with reference to the accompanyingdiagrammatic drawing which in part shows a machine for:v manufacturingplastic foil covered paper (paper-plastic laminate). Thus, in thedrawing there are shown a rubber roll 1 and a metallic roll 2cooperating therewith, which is adapted to allow the passagetherethrough, in a manner not shown, of a cooling medium so as to act asa cooling roll. A paper web 3 can be passed across parts of the machinenot shown on to the rubber roll 1 and intothe nip between this roll andthe cooling roll 2. Straight above the rolls there is provided adownwardly directed extruder nozzle 4 which is associated with anextrusion machine, otherwise not illustrated, for extruding athermoplastic, such as polystyrene, in the shape of a foil 5. As itemerges from the nozzle, this foil 5 moves straight down into the nipbetween the rolls 1 and 2, and there meets the paper web 3. Owing to itsstill hot plastic condition and the pressure exerted by the rolls thefoil of plastic is bonded to the paper web, so that a plastic foilcovered paper is obtained. The device described in principle above isgenerally known and used.

In this device the length of the path from the nozzle 4 to the nipbetween the rolls 1 and 2 cannot always, for constructional reasons, bemade so short as would be desirable to avoid excessive cooling of thefoil, before it is brought together with the paper Web. The bonding ofthe foil to the latter is under such conditions open to the risk of notbeing perfect. It is true that the provision of bright heat-reflectingmetallic screens on either side of said length of path, according to theproposal mentional in the intro duction, efiiciently neutralizes thecooling of the foil, but precisely for this reason it causes anoxidation on both sides of the foil of plastic, while the latter travelsthe relatively long way down to the paper web.

According to the present invention, a heat-reflecting metallic screen 6,eg from aluminum, is provided on one side of the above-mentioned pathfacing the side of'the foil of plastic 5 which is to contact the paperWeb 3, while on the otherside of the path there is provided a blackenedmetallic screen 7 which accordingly faces the free side of the foil ofplastic 5 and acts as an absolutely black and, therefore, heat-absorbingbody. The metallic screen 6 is besides heat insulated in relation to theenvironment by being mounted with its back on a heat insulating plate 8to counteract heat losses which arise by the dissipation of part of theradiation heat received by the screen. The blackened metallic screen 7,on the other hand, has to be in heat conducting relationship with theenvironment and should preferably be cooled for example by means of acirculating cooling medium (not shown) to increase the heat absorbingcapacity of this screen.

truder nozzle 4 that the undesirable oxidation on this side is avoided.

That which is claimed is:

1. The method of producing a web of plastic coated paper comprising thesteps of: extruding a plastic foil through a space between a reflectormeans and a blackened body, reflecting heat radiated from said foil backonto one side of said foil by means of said reflector means to maintainsaid one side at an elevated temperature, maintaining the other side ofsaid foil at a low temperature by absorbing heat by means of saidblackened body from said other side of said foil prior to laminating toa web of paper and laminating said one side of said foil to a web ofpaper.

References Cited UNITED STATES PATENTS 3,075,868 1/1963 Long 156-244X3,077,428 2/ 1963 Heuser et al 156--244X 5 3,165,432 1/ 1965 Plashett1-5 6244 FOREIGN PATENTS 725,!127 1/ 1966 Canada 15 6-244 BENJAMIN R.PADGE'IT, Primary Examiner H. E. BEHREND, Assistant Examiner

